This project is directed towards the development of computerized, noninvasive measurement system designed to evaluate motor disorders in a clinical neurologic setting. A method has been developed that operationally defines two human motor subsystems, referred to as the feed-forward-based volitional motor system and the feedback-based reflexive motor system. The measurement system records and identifies abnormalities in each motor subsystem and in the coordination of the subsystems. While previous methods measure either the volitional or reflexive system, the current method evaluates both and measures the coordination between the two systems. Substantial previous development has resulted in a simple and robust procedure allowing measurement of reflex gain and volitional output during visually guided tracking. Measurement of motor subsystem coordination by this method has identified significant differences between age-matched normal and bradykinetic parkinsonian subjects (p<0.001, Student's t-test, N=30). Thus, one example of defective central coordination of the volitional and reflexive motor systems has been described and mechanism of bradykinesia provided (Johnson et al, 1990). This grant will fund the extension of the described methodology, first by expanding the utility of parkinsonian testing to the evaluation of therapeutic response, and secondly by documenting motor control pathophysiology for a range of motor disorder diagnostic categories. Development of the potential for therapeutic evaluation and diagnosis of motor disorders will justify the clinical utility for quantitative motor evaluation. These extensions will expand the physiologic database, drive software development, and define the market for this methodology.